Polar IR-HARQ Encoding With XOR Inner Coding for Better Decoding
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Solution Overview
Problem
Existing hybrid ARQ (HARQ) transmission systems in wireless networks face challenges in implementing incremental redundancy (IR) schemes effectively with polar codes, as their construction is not straightforward, leading to suboptimal performance compared to Chase combining.
Innovation Solution
The proposed solution involves a multi-phase encoding system that includes an outer encoder, a set of polar sub-encoders for polar encoding, and an inner encoder performing Exclusive Or (XOR) operations to generate code bits for incremental redundancy HARQ transmissions, enhancing channel capacity and decoding performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If incremental redundancy (IR) schemes are implemented with polar codes in existing HARQ transmission systems, then decoding performance and channel capacity should improve, but the construction complexity increases significantly making it non-straightforward
Solution Approach 1:
The polar code construction is divided into multiple stages: initial polar code generation, information bit selection based on channel capacity, and incremental redundancy generation through systematic encoding. This segmentation makes the complex construction process manageable and implementable while maintaining improved decoding performance.
Solution Approach 2:
Channel capacity is pre-calculated for each bit channel before encoding, and information bit positions are predetermined based on these capacities. This preliminary action simplifies the actual encoding process during HARQ transmissions, reducing real-time construction complexity while ensuring optimal performance.
2Reliability
If polar encoding is performed for each HARQ transmission with incremental redundancy, then channel capacity increases, but the encoding and decoding complexity increases making it less efficient than Chase combining
Solution Approach 1:
Different encoding approaches are applied to different parts of the code: systematic bits are transmitted directly while parity bits are generated through polar encoding. This local differentiation allows efficient encoding where needed while maintaining channel capacity improvements where required.
Solution Approach 2:
The coding rate is dynamically adjusted across HARQ transmissions by changing the number of information bits and parity bits transmitted. This parameter change enables efficient use of channel resources while achieving incremental redundancy benefits without constant full polar encoding complexity.
3Reliability
If a multi-phase encoding system with outer encoder, polar sub-encoders, and inner encoder is used, then decoding performance improves beyond Chase combining, but the device complexity and implementation difficulty increase
Solution Approach 1:
The encoding system uses a nested structure with outer encoder containing multiple polar sub-encoders, which in turn contain inner encoders. This nesting organizes the complexity hierarchically, making the system manageable while achieving superior decoding performance through multiple layers of error correction.
Solution Approach 2:
Multiple encoding functions (outer encoding, polar encoding, inner encoding) are merged into a unified HARQ transmission system. This integration allows the system to achieve the performance benefits of each encoding layer while managing overall complexity through coordinated operation.
Data Source
AI summary
Encoding System for Incremental Redundancy for Hybrid ARQ for Wireless Networks A technique is provided for encoding, by an outer encoder, a set of information bits; performing, by each polar sub-encoder of a set of polar sub-encoders, polar encoding of bits received from the outer encoder for a corresponding incremental redundancy (IR) hybrid ARQ (HARQ) transmission; and performing, by an inner encoder, for each bit input to the inner encoder from one of the polar sub-encoders for the HARQ transmission, an Exclusive Or (XOR) operation with another bit, to generate a set of code bits for an IR-HARQ transmission over a channel.